88 DWIGHT 



feather itself breaks from the apex. The follicle is pulpy, dark 

 and bluish in appearance owing to the developing feather within, 

 the quill of which, after it is grown, remaining pulpy until one 

 or two of the adjacent quills have reached maturity. The re- 

 mains of the follicle persist in the form of a scaly sheath at the 

 base of each quill until several of the new feathers are fully 

 grown and often much longer. This development of the new 

 feather is not peculiar to the primaries, but is true of every other 

 feather on a bird. Before, however, the follicle of the proximal 

 primary has opened, the primary adjacent regularly falls, closely 

 followed by its upper covert. It probably falls at very nearly 

 the same time as the proximal in many cases and even in ad- 

 vance of it in a few, as may be inferred from the relative length 

 of the two new feathers, but as a rule the order is the one indi- 

 cated. Both are out of their follicles before the next adjacent, 

 and its covert falls, and this is followed in order by the more 

 distal primaries one after another. At no time is a gap left of 

 more than one or two whole feathers at most and perhaps one 

 or more partly grown so that a Passerine bird is never much 

 hampered in its flight. 



From the examination of specimens it is impossible to deter- 

 mine the exact time required for a complete renewal of this 

 most important row of flight-feathers which is usually the first 

 to be affected by the moult in adults although outstripped in 

 development by some of the other areas. I should estimate the 

 time at about one month or probably a little longer. In exten- 

 sive series of a few species, I find that the period between the 

 earliest date of a specimen showing loss of the proximal primary 

 and the earliest date of a specimen showing the distal primary 

 fully grown varies between a month and six or eight weeks. 



The primaries are rarely moulted more than once in a year. 

 Adults and year-old birds at the end of the breeding season 

 both male and female always renew them. In a few species, all 

 the primaries are again renewed by moult in the winter or early 

 spring. Young birds of a few species moult these feathers in 

 acquiring their autumnal or first winter dress, but the majority 

 retain them until the moult following the first breeding season. 



